This invention relates to terpolymerization. It relates in particular to terpolymers of ethylene, 1-pentene and a third alpha olefin, to a process for producing such terpolymers, and to a method of preparation of a prepolymer.
According to a first aspect of the invention, there is provided a terpolymer of ethylene, 1-pentene and a further alpha olefin (xe2x80x9cxcex1-olefinxe2x80x9d) which differs as regards its total number of carbon atoms, by more than 1 unit from 1-pentene.
In other words, according to the first aspect of the invention, there is provided a terpolymer which comprises a polymerization product obtained by polymerizing at least ethylene, 1-pentene and a further alpha olefin (xe2x80x9cxcex1-olefinxe2x80x9d) which differs as regards its total number of carbon atoms, by more than 1 unit from 1-pentene.
The Inventors have discovered that known art relating to the copolymerization of ethylene with different alpha olefins, and known art relating to the terpolymerization of ethylene with alpha olefins cannot be applied directly to the terpolymerization of ethylene with 1-pentene and a third alpha olefin. On the contrary, in the terpolymerization of ethylene with 1-pentene and the further xcex1-olefin according to the invention, surprising application terpolymers can be obtained with unexpected domains of fundamental properties. It is known from the art that polymers of ethylene, in the same domain of density, exhibit appropriate application properties derived from the density, with known correction mainly due to differences in the melt flow index and the index of polydispersity. The Inventors have, however, surprisingly found that terpolymers of ethylene with 1-pentene and a further or third alpha olefin according to this invention may have the same domain of density and while in the same domain of melt flow index and/or domain of polydispersity may, however, have very different and surprising application properties.
The Inventors have even more surprisingly discovered that within the family of. the terpolymers of ethylene with 1-pentene and a third alpha olefin according to this invention, particular families with even more surprising application properties can be obtained. Thus, a terpolymer of ethylene with 1-pentene and a further xcex1-olefin as hereinbefore described can have unexpectedly different properties when compared with a terpolymer of ethylene with one pentene and a further xcex1-olefin differing, as regards its total number of carbon atoms, from 1-pentene and having fewer carbon atoms than 1-pentene.
The properties of the terpolymer of the invention are determined mainly by the ratio or proportion of ethylene to the combination of 1-pentene and the further xcex1-olefin in the terpolymer, and by the ratio or proportion of 1-pentene to the further xcex1-olefin. In other words, the properties of the terpolymer, based on the ethylene: the sum of the total comonomer content, on a molar basis, can be altered by varying the molar ratio of the 1-pentene: further xcex1-olefin. In this manner, a large number of particular terpolymers can be obtained with large range of application properties controlled between certain limits. Typical applications of the terpolymer include extrusions, blow moulding and injection moulding.
The ratio of the molar proportion of ethylene to the sum of the molar proportions of 1-pentene and the further xcex1-olefin may be between 99,9:0,1 and 90:10.
The ratio of the molar proportion of 1-pentene to that of the further xcex1-olefin may be between 0,01:99,99 and 99,99:0,01. The preferred third xcex1-olefin content of the terpolymer, based on the 1-pentene content thereof, is greater than 10% by mass and, most preferably, greater than 20% by mass.
The third alpha olefin may be any alpha olefin having a total number of carbon atoms greater than 6 and less than 10 except alpha olefins with a branch directly linked to the double bond. Preferred are linear alpha olefins. The most preferred are alpha olefins with a total number of carbon atoms equal to or less than 8.
The Inventors have surprisingly discovered that terpolymers of ethylene, 1-pentene and a further xcex1-olefin wherein the number of carbon atoms of the third alpha olefin differs 3 units or less from 1-pentene often have superior application properties and a better balance of properties to those where the number of carbon atom differs by more than 3 units from 1-pentene.
In particular, the further alpha olefin may be 1-octene. The terpolymer of this aspect of the invention will thus be a terpolymer of ethylene, 1-pentene and 1-octene.
The terpolymer of ethylene, 1-pentene and 1-octene may have the following properties:
(a) A melt flow rate, as measured according to ASTM D 1238, in the range of about 0,01 to about 100 g/10 min; and/or
(b) A density as measured according to ASTM D 1505, in the range 0,890 to about 0,950.
In an even more particular case, this terpolymer may be such that when it is bottom blown into a film having a thickness of 30xcexc, the film complies with the following requisites:
(i) An impact strength, as measured according to ASTM D 1709, of greater than 60 g: and/or
(ii) A tear strength, as measured according to ASTM 1922, of greater than 2,3 g/xcexcm in the machine direction (MD) and greater than 11 g/xcexcm in the transverse direction (TD).
In another particular case, the terpolymer of ethylene, 1-pentene and 1-octene may be such that when injection moulded according to ASTM D 647, it has the following properties:
(a) A melt flow rate, as measured according to ASTM D 1238, in the range of about 0,01 to about 100 g/10 min; and/or
(b) A density as measured according to ASTM D 1505, in the range 0,890 to about 0,950;
(c) an Izod notched impact strength, as measured according to ASTM D 256, of between 5 and 50 kJ/m2;
(d) a tensile strength at yield, as measured according to ASTM D 256 M, of between 7,5 and 15 MPa; and
(e) a modulus, as measured according to ASTM D 256 M, of between 150 and 600 MPa.
According to a second aspect of the invention, there is provided a terpolymer of ethylene, 1-pentene and a further alpha olefin (xe2x80x9cxcex1-olefinxe2x80x9d) which, as regards its total number of carbon atoms, differs by 1 unit from 1-pentene and has more carbon atoms than 1-pentene, and which, when injection moulded according to ASTM D 647, complies with the following requisites:
(a) a melt flow rate, as measured according to ASTM D 1238, in the range of about 0,01 to about 100 g/10 min; and/or
(b) a density as measured according to ASTM D 1505, in the range 0,890 to about 0,950;
(c) an Izod notched impact strength, as measured according to ASTM D 256, of between 5 and 65 kJ/m2;
(d) a tensile strength at yield, as measured according to ASTM D 256 M, of between 9 and 25 MPa; and
(e) a modulus, as measured according to ASTM D 256 M, of between than 200 and 1000 MPa.
In other words, according to the second aspect of the invention, there is provided a terpolymer which comprises a polymerization product obtained by polymerizing at least ethylene, 1-pentene and a further alpha olefin (xe2x80x9cxcex1-olefinxe2x80x9d) which, as regards its total number of carbon atoms, differs by 1 unit from 1-pentene and has more carbon atoms than 1-pentene, and which, when injection moulded according to ASTM D 647, complies with the following requisites:
(a) a melt flow rate, as measured according to ASTM D 1238, in the range of about 0,01 to about 100 g/10 min; and/or
(b) a density as measured according to ASTM D 1505, in the range 0,890 to about 0,950;
(c) an Izod notched impact strength, as measured according to ASTM D 256, of between 5 and 65 kJ/m2;
(d) a tensile strength at yield, as measured according to ASTM D 256 M, of between 9 and 25 MPa; and
(e) a modulus, as measured according to ASTM D 256 M, of between than 200 and 1000 MPa.
This alpha olefin may thus be 1-hexene. The terpolymer of this aspect of the invention is thus a terpolymer of ethylene, 1-pentene and 1-hexene.
This terpolymer may also be such that when it is bottom blown into a film having a thickness of 30xcexc, the film complies with the following requisites:
(i) An impact strength, as measured according to ASTM D 1709, of greater than 60 g; and/or
(ii) a tensile strength at yield, as measured according to ASTM D 882 higher than 7 MPa in the machine direction (MD) higher than 8 MPa in the transverse direction.
According to a third aspect of the invention, there is provided a terpolymer of ethylene, 1-pentene and a further alpha olefin (xe2x80x9cxcex1-olefinsxe2x80x9d) which, as regards its total number of carbon atoms, differs by 1 unit from 1-pentene and has fewer carbon atoms than 1-pentene.
In other words, according to the second aspect of the invention, there is provided a terpolymer which comprises a polymerization product obtained by polymerizing at least ethylene, 1-pentene and a further alpha olefin (xe2x80x9cxcex1-olefinxe2x80x9d) which, as regards its total number of carbon atoms, differs by 1 unit from 1-pentene and has fewer carbon atoms than 1-pentene.
The properties of the terpolymer according to the third aspect of the invention are determined mainly by the ratio or proportion of ethylene to the combination of 1-pentene and the further xcex1-olefin in the terpolymer, and by the ratio or proportion of 1-pentene to the further xcex1-olefin. In other words, the properties of the terpolymer based on the ethylene: the sum of the total comonomer content, on a molar basis, can be altered by varying the molar ratio of 1-pentene: further xcex1-olefin. In this manner a large number of particular terpolymers can be obtained with a large range of application properties controlled between certain limits.
As before, the ratio of the molar proportion of ethylene to the sum of the molar proportions of 1-pentene and the further xcex1-olefin may be between 99,9:0,1 and 90:10.
The ratio of the molar proportion of 1-pentene to that of the further xcex1-olefin may be between 0,01:99,99 and 99,99:0,01. The preferred third xcex1-olefin content of the terpolymer, based on the 1-pentene content thereof, is greater than 10% by mass and, most preferably, greater than 20% by mass.
The further xcex1-olefin thus, in the third aspect of the invention, is 1-butene. Thus, the terpolymer of the third aspect of the invention is a terpolymer of ethylene, 1-pentene and 1-butene.
In particular the terpolymer of ethylene, 1-pentene and 1-butene may have the following properties:
(a) A melt flow rate, as measured according to ASTM D 1238, in the range of about 0,01 to about 100 g/10 min; and/or
(b) A density, as measured according to ASTM D 1505, in the range 0,890 to about 0,950.
More particularly, this terpolymer may be such that, when it is bottom blown into a film having a thickness of 30xcexc, the film complies with the following requisites:
(i) A tensile strength at break, as measured according to ASTM D 882, of greater than 25 MPa in the machine direction (MD) and greater than 20 MPa in the transverse direction (TD); and/or
(ii) A tensile strength at yield, as measured according to ASTM D 882, of greater than 12 MPa in the machine direction (MD) and greater than 11 MPa in the transverse direction (TD).
In another particular case the terpolymer of ethylene, 1-pentene and 1-butene may be such that, when injection moulded according to ASTM D 647, it complies with the following properties:
(a) A melt flow rate, as measured according to ASTM D 1238, in the range of about 0,01 to about 100 g/10 min; and/or
(b) A density as measured according to ASTM D 1505, in the range 0,890 to about 0,950.
(c) an Izod notched impact strength, as measured according to ASTM D 256, of between 5 and 40 kJ/m2.
(d) a tensile strength at yield, as measured according to ASTM D 256 M, of between 5 and 20 MPa
(e) a modulus as measured according to ASTM D 256 M, of between 100 and 500 MPa.
In particular, the terpolymers according to the first, second and third aspects of the invention may be those obtained by reacting ethylene, 1-pentene and the further xcex1-olefin in one or more reaction zones, while maintaining in the reaction zone(s) a pressure in the range between atmospheric pressure and 200 kg/cm2 and a temperature between ambient and 300xc2x0 C., in the presence of a suitable catalyst or catalyst system, particularly a Ziegler-Natta catalyst or catalyst system.
The Inventors have also found out that in the terpolymerization of ethylene with 1-pentene and a further alpha olefin, even more particular terpolymers are obtained when different particular processes are employed to produce terpolymers of ethylene with 1-pentene and the further alpha olefin.
Thus, according to a fourth aspect of the invention, there is provided a process for producing a terpolymer, which process comprises reacting a reaction mixture comprising ethylene, 1-pentene and a further xcex1-olefin which differs, as regards its total number of carbon atoms, by more than 1 unit from 1-pentene in one or more reaction zones, while maintaining the reaction zone(s) at a pressure between atmospheric pressure and 200 kg/cm2, and at a temperature between ambient and 300xc2x0 C., in the presence of a catalyst or a catalyst system comprising a catalyst and a cocatalyst, with the reaction being effected in a slurry phase, a gas phase or a solution phase.
Also, according to a fifth aspect of the invention, there is provided a process for producing a terpolymer, which process comprises reacting a reaction mixture comprising ethylene, 1-pentene, and a further xcex1-olefin which, as regards its total number of carbon atoms, differs by 1 unit from 1-pentene and has fewer carbon atoms than 1-pentene, in one or more reaction zones, while maintaining the reaction zone(s) at a pressure between atmospheric pressure and 200 kg/cm2, and at a temperature between ambient and 300xc2x0 C., in the presence of a catalyst or a catalyst system comprising a catalyst and a cocatalyst, with the reaction being effected in a slurry phase, a gas phase or a solution phase.
Further, according to a sixth aspect of the invention, there is provided a process for producing a terpolymer, which process comprises reacting a reaction mixture comprising a ethylene, 1-pentene, and a further xcex1-olefin which, as regards its total number of carbon atoms, differs by 1 unit from 1-pentene and has more carbon atoms than 1-pentene, in one or more reaction zones, while maintaining the reaction zone(s) at a pressure between atmospheric pressure and 200 kg/cm2, and at a temperature between ambient and 300xc2x0 C., in the presence of a catalyst or a catalyst system comprising a catalyst and a cocatalyst, with the reaction being effected in a gas phase or a solution phase.
The reaction is thus carried out in one or more reaction zones, which may be provided in a single stage reactor vessel or by a chain of two or more reaction vessels.
The reaction can be effected in a batch fashion, with the 1-pentene and the further xcex1-olefin being added simultaneously at the start of the reaction while the ethylene is added continuously during the course of the reaction, with no product being removed during the reaction. Instead, the reaction can be effected in a batch fashion, with the 1-pentene and the further xcex1-olefin being added simultaneously with the ethylene and continuously or discontinuously during the course of the reaction, with no product being removed during the reaction. Instead, the reaction can be effected in a batch fashion, with either 1-pentene or the further xcex1-olefin being added at the start of the reaction while ethylene is added continuously during the reaction and a continuous or discontinuous supply of the monomer which was not added at the beginning of the reaction is provided, with no product being removed during the reaction.
The reaction can, however, instead be effected in a continuous fashion, with the ethylene being added continuously and the 1-pentene and the further xcex1-olefin being added together or separately, continuously or discontinuously, during the course of the reaction, and the terpolymer product continuously being withdrawn from the reaction zone.
Terpolymers obtained from the process by using a particular feed composition and under particular reaction conditions have a random distribution which is determined mainly by the different reactivities of the monomers. This provide once more a unique tool for obtaining a large variety of ethylene, 1-pentene and further xcex1-olefin terpolymers whose properties are mainly controlled by their composition and non-uniformity.
The molecular weight of the resultant random terpolymer can be regulated by hydrogen addition to the reaction zone during the reaction. The greater the amount of hydrogen added, the lower will be the molecular weight of the random terpolymer.
The terpolymerization is preferably performed in a substantially oxygen and water free state, and in the presence or absence of an inert saturated hydrocarbon
The terpolymerization reaction according to the fourth and fifth aspects of the invention may thus be carried out in slurry phase, solution phase or vapour phase, with slurry phase polymerization being preferred.
Thus, in one embodiment of the fourth and fifth aspects of the invention, a slurry polymerization process is used. The further xcex1-olefin may then, in particular, be 1-octene or 1-butene.
When slurry phase polymerization is used, the catalyst will thus be in solid particulate form, and preferably comprises a Ziegler-Natta catalyst. Thus, the ethylene, 1-pentene and the further xcex1-olefin will be polymerized in a suspension state in the presence of the Ziegler-Natta catalyst in solid particulate form and which is suspended in a slurrying or suspension agent.
The Ziegler-Natta catalyst may be that obtained by contacting magnesium chloride with titanium tetrachloride in the presence of a plurality of alcohols.
Thus, the magnesium chloride is the support of the catalyst. The magnesium chloride may be used in the form of anhydrous or partially anhydrized magnesium chloride providing that the anhydrization is effected in such a manner that no anhydrization agent remains in the anhydrized magnesium chloride which is further used to prepare the catalyst. The magnesium chloride may have a water content of between 0,02 mole of water/1 mole of magnesium chloride and 2 mole of water/1 mole of magnesium chloride. More preferably, the water content of the magnesium chloride may, in one. particular case, be 1,5% by mass, and in a second particular case, may be 5% by mass.
The anhydrous or partially anhydrized magnesium chloride is preferably activated prior to contacting or loading it with the titanium tetrachloride.
The activation of the anhydrous or partially anhydrized magnesium chloride may be performed under inert conditions, ie in a substantially oxygen and water free atmosphere, and in the absence or presence of an inert saturated hydrocarbon carrier liquid. Preferred inert saturated hydrocarbon carrier liquids, when present, are aliphatic or cyclo-aliphatic liquid hydrocarbons, such as hexane and heptane.
The magnesium chloride or support activation may be performed in two steps (a1) and (a2).
In step (a1), an ether may be added under inert conditions to a suspension of the magnesium chloride in the inert hydrocarbon carrier liquid or to the magnesium chloride in powder form. The ether may be selected from linear ethers having a total number of carbon atoms between 8 and 16. The most preferred ethers are: di-butyl ether and di-pentyl ether. The molar ratio of the magnesium chloride to the ether may be between 0,3:1 and 3:1, with the preferred molar ratio being 1:1 to 2,5:1. The resultant mixture or suspension may be stirred for a period of 10 minutes to 24 hours at room temperature. The preferred stirring time is 1 to 12 hours. The preferred temperature for mixing the ether with the magnesium chloride to prepare the partially activated magnesium chloride is 40xc2x0 C. to 140xc2x0 C.
In the second step (a2) an alkyl aluminium compound may be added, preferably in dropwise fashion, to the partially activated magnesium chloride. Typical alkyl aluminium compounds which can be used are those expressed by the formula AlR3 wherein R is an alkyl radical or radical component having 1 to 10 carbon atoms. Specific examples of suitable alkyl aluminium compounds which can be used are: tri-butyl aluminium, tri-isobutyl aluminium, tri-hexyl aluminium and tri-octyl aluminium. The most preferred organo-aluminium compounds is triethyl aluminium. The molar ratio of the alkyl aluminium compound to the anhydrous magnesium chloride may be between 1:1 and 6:1. The preferred molar ratio of the alkyl aluminium compound to the anhydrous magnesium chloride is 4:1 to 5:1. The proportions of the alkyl-aluminium compound and partially activated magnesium chloride used may be such that formula (1) is complied with:
A greater than B+C+Dxe2x80x83xe2x80x83(1)
where
A represents the total moles of the alkyl aluminium compound;
B represents the total moles of magnesium chloride used;
C represents the total moles of ether used; and
D represents the total moles of water present, being the sum of the water of hydration associated with the magnesium chloride and any traces of water in the carrier liquid.
The loading of the activated magnesium chloride or support with the titanium tetrachloride may be performed in two steps (b1) and (b2).
In the first step (b1), to the support, after thorough washing thereof with hexane, is added the plurality of alcohols under stirring. The alcohols may be added separately. However, they are preferably added as a multicomponent mixture. Each alcohol may be selected from the range of alcohols having 2 to 8 carbon atoms. A dicomponent alcohol mixture or a three component alcohol mixture can thus be used. A three component mixture of alcohols is preferred. The most preferred method is to select, in a tricomponent alcohol mixture, the three alcohols having the same number of carbon atoms as three monomers used in the process of producing a terpolymer wherein the catalyst, the product of this catalyst preparation, is used. Examples of preferred alcohol mixtures for use in the catalyst preparation are: a mixture of ethanol, butanol and pentanol; a mixture of ethanol, hexanol and pentanol; or a mixture of ethanol, octanol and pentanol.
The molar ratio of the alcohol mixture to the initial magnesium chloride used may be between 0,4:1 and 4:1. However the preferred molar ratio of the alcohol mixture to the initial magnesium chloride is 0,8:1 to 2,5:1.
The molar ratio between the two alcohols in a dicomponent mixture can be 100:1 to 1:100; however, the preferred molar ratio between the two alcohols is 1:1.
The molar ratio between the three alcohols in a three component alcohol mixture can vary widely, but preferably is about 1:1:1.
The stirring time may be between 1 min and 10 hours, preferably about 3 hours.
The temperature range can be between 0xc2x0 C. and the lower of the boiling point of the any one of the alcohols of the multicomponent alcohol mixture or the solvent used in this step of the catalyst preparation.
In one embodiment, the amounts of the alcohols used in this step may be such that formula (2) is complied with:
[A] less than [Al]xe2x80x83xe2x80x83(2)
where [A] represents the total moles of alcohol added and [Al] is the measured moles of aluminium present in the activated magnesium chloride-containing slurry.
In another embodiment, the amounts of the alcohols used in this step may be such that formula (3) is complied with:
[A] less than 2[Al]/3xe2x80x83xe2x80x83(3)
where [A] and [Al] are as hereinbefore defined.
In yet another embodiment, the amounts of the alcohols used in this step may be such that formula (4) is complied with:
[A] less than [Al]/3xe2x80x83xe2x80x83(4)
where [A] and [Al] are as hereinbefore defined.
In the second step (b2), TiCl4 may be added to the support/alcohol mixture, the mixture or slurry stirred under ref lux and finally left to cool, eg for about 24 hours. The catalyst obtained may be thoroughly washed, eg with hexane.
The molar ratio of TiCl4 employed in this step to the initial magnesium chloride may be from about 2:1 to about 20:1, preferably about 10:1.
The co-catalyst, when present, may be, or comprise, an organo aluminium compound. Typical organo-aluminium compounds which can be used are compounds expressed by the formula AlRmX3xe2x88x92m wherein R is a hydrocarbon component of 1 to 15 carbon atoms, X is a halogen atom, and m is a number represented by 0 less than mxe2x89xa63. Specific examples of suitable organo aluminium compounds which can be used are: a trialkyl aluminium, a trialkenyl aluminium, a partially halogenated alkyl aluminium, an alkyl aluminium sesquihalide, an alkyl aluminium dihalide. Preferred organo aluminium compounds are alkyl aluminium compounds, and the most preferred is triethylaluminium. The atomic ratio of aluminium to titanium in the catalyst system may be between 0,1:1 and 10000:1, preferably between 1:1 and 5000:1.
Preferred slurrying or suspension agents are aliphatic or cyclo-aliphatic liquid hydrocarbons, with the most preferred being hexane and heptane.
The Inventors have surprisingly found that the particular way in which the catalyst complex is supplied to the reaction zone when using the catalyst as hereinbefore prepared strongly affects the catalyst performance in particular aspects of the process according to this invention.
Particular aspects of the process according to this invention are distinguished by whether the activation step of the catalyst with the cocatalyst to obtain the catalyst system is performed directly in the reaction zone or in a separate activation unit.
Particular aspects of the process according to this invention are distinguished by whether the catalyst system is supplied to the reaction zone at xe2x80x9cthe optimum ageing timexe2x80x9d, or at xe2x80x9cconstant activityxe2x80x9d time.
The Inventors have found that a particular catalyst prepared according to the method described above and designed for a particular process of terpolymerization of ethylene with 1-pentene, and 1-butene or 1-octene, or for a process for the terpolymerization of ethylene with 1-pentene and another alpha olefin and even more generally for homopolymerization, copolymerization, terpolymerization or multiple polymerization of olefins, exhibit particular activation/deactivation kinetics when put in contact with the cocatalyst, the organo-aluminium compound.
More particularly, the catalyst prepared according to the method as hereinbefore described, may reach the highest activity in the polymerization of the olefins or monomers, and even more particularly in the terpolymerization of ethylene with 1-pentene, and 1-butene or 1-octene or in the terpolymerization of ethylene with 1-pentene and another alpha olefin, after a particular time elapsed from the moment the catalyst is put in contact with the cocatalyst.
For each particularly prepared catalyst xe2x80x9cthe optimum ageing timexe2x80x9d, xOATy, is defined as the time, expressed in minutes, which has elapsed from the moment the catalyst and the cocatalyst are put in contact with each other, until they reach maximum activity for the polymerization of a specific monomer or monomers, y, at a specific temperature, x, indicated in 0xc2x0 C., in a standard slurry batch polymerization performed in polymerization grade n-heptane at a total constant pressure of 15 kg/cm2 with a partial pressure of hydrogen of 2 kg/cm2. The term, y, can be a monomer or a mixture of two, three or more monomers or olefins represented by the letter C followed by a number representing the total number of carbon atoms of the alpha olefin employed. When more than one monomer is used, such as in the case of co-, ter- or multiple polymerization, then, for each monomer or xcex1-olefin used, the letter C combined with the number representing the total carbon atoms of that alpha olefin is used, with these designations being connected by the sign +, with two of them representing the particular copolymerization and with three of them representing the particular terpolymerization.
Thus 50OATC2+C4+C5 represents an OAT for a temperature of 50xc2x0 C. and a mixture of ethylene, butene-1 and pentene-1.
However, for practical reasons, a standard measurement of OAT for ethylene at 80xc2x0 C. may be used.
For each particularly prepared catalyst xe2x80x9cconstant activity time xe2x80x9cxCATyxe2x80x9d, is defined as the time, expressed in minutes, which has elapsed from the moment the catalyst and the cocatalyst are put in contact with each other until they reach a constant activity for the polymerization of a specific monomer or monomers, y, at a specific temperature, X, indicated in xc2x0 C., in a standard slurry batch polymerization performed in polymerization grade n-heptane at a total constant pressure of 15 kg/cm2 with a partial pressure of hydrogen of 2 kg/cm2. The term, y, can be a monomer or a mixture of two, three or more monomers or olefins represented by the letter C followed by a number representing the total number of carbon atoms of the alpha olefin employed. When more than one monomer is used, such as in the case of co-, ter- or multiple polymerization, then, for each monomer or xcex1-olefin used, the letter C combined with the number representing the total carbon atoms of that alpha olefin is used, with these designations being connected by the sign +, with two of them representing the particular copolymerization and with three of them representing the particular terpolymerization.
Thus 50CATC2+C4+C5 represents a CAT for a temperature of 50xc2x0 C. and a mixture of ethylene, butene-1 and pentene-1.
However, for practical reasons, a standard measurement of CAT for ethylene at 80xc2x0 C. may be used.
For each particularly prepared catalyst xe2x80x9cLimit activity time, xe2x80x9cxLATyxe2x80x9d, is defined as the time, expressed in minutes, which has elapsed from the moment the catalyst and the cocatalyst are put in contact with each other until they reach an activity lower than a productivity of 10000 g of polymer/g of catalyst/hour, for the polymerization of a specific monomer or monomers, y, at a specific temperature, x, indicated in xc2x0 C., in a standard slurry batch polymerization performed in polymerization grade n-heptane at a total constant pressure of 15 kg/cm2 with a partial pressure of hydrogen of 2 kg/cm2. The term, y, can be a monomer or a mixture of two, three or more monomers or olefins represented by the letter C followed by a number representing the total number of carbon atoms of the alpha olefin employed. When more than one monomer is used, such as in the case of co-, ter- or multiple polymerization, then, for each monomer or xcex1-olefin used, the letter, C, combined with the number representing the total carbon atoms of that alpha olefin is used, with these designations being connected by the sign +, with two of them representing the particular copolymerization and with three of them representing the particular terpolymerization.
Thus 50L LATC2+C4+C5 represents an LAT for a temperature of 50xc2x0 C. and a mixture of ethylene, butene-1 and pentene-1.
However, for practical reasons, a standard measurement of LAT for ethylene at 80xc2x0 C. may be used.
Thus, in a particular case of the slurry phase polymerization, the cocatalyst may first be supplied to the reaction zone, and the catalyst then supplied thereto after a time interval. In another particular case, the cocatalyst and the catalyst may be supplied simultaneously to the reaction zone. In both these cases, the residence time of the reaction mixture may preferentially be selected to be less than LAT.
In still another case of this aspect of the invention the catalyst system, after being prepared separately in an activation zone or unit, is supplied to the reaction zone at OAT. In these cases, the sum of the residence time of the catalyst in the activation unit and the residence time of the catalyst in the reaction zone, may preferentially be selected to be less than LAT. When the reaction is carried out in more than one reaction zone, which may be provided in a single stage reactor vessel or by a chain of two or more reaction vessels, then two cases of this particular aspect of the invention can be distinguished.
In one particular case, the sum of the residence time of the catalyst in the activation unit and the residence time of the catalyst in the first reaction zone may be OAT+TR1, where TR1 is the time elapsed since OAT up to the moment the catalyst reaches a decrease of activity of less than 25% of the activity at OAT.
In another particular case, the sum of the residence time of the catalyst in the activation unit and the residence time of the catalyst in the first reaction zone may be OAT+TR22, where TR2 is the time selected in such a way that OAT+TR2 is less than LAT, preferentially less than xc2xd LAT and provided that the sum of the residence time. of the catalyst in the activation unit and the residence time of the catalyst in all reaction zones is less than LAT.
In still another particular case of this aspect of the invention, the catalyst system may be prepared in a separate catalyst activation unit and supplied to the reaction zone at CAT. In these cases, the sum of the residence time of the catalyst in the activation unit and the residence time of the catalyst in the reaction unit may preferentially be selected to be less than LAT.
In another embodiment of this aspect of the invention, the catalyst system is supplied to the reaction zone at any other time less than LAT providing that the sum of the residence time of the catalyst in the activation unit and the residence time of the catalyst in all reaction zones is less than LAT.
In one embodiment of the slurry polymerization process, the further xcex1-olefin may thus be 1-butene.
In the loading step of the titanium tetrachloride on the activated support in the preparation of the Ziegler-Natta catalyst which is used, a mixture of ethanol and butanol or a mixture of ethanol, butanol and pentanol may then be used.
While the reaction temperature can be in the range of ambient to 120xc2x0 C., it is preferably in the range of 50xc2x0 C. to 100xc2x0 C. and most preferably in the range of 60xc2x0 C. to 90xc2x0 C.
While the pressure can be in the range of atmospheric pressure to 60 kg/cm2, it is preferably in the range of 3 kg/cm2 to 30 kg/cm2, still more preferably in the range of 4 kg/cm2 to 18 kg/cm2.
The parameters of the terpolymerization reaction of ethylene, 1-pentene and 1-butene in the slurry phase polymerization may be such that the resultant terpolymer of ethylene, 1-pentene and 1-butene satisfies the requisites or properties hereinbefore set out for such a terpolymer.
In another embodiment of the slurry polymerization process, the further xcex1-olefin may thus be 1-octene.
In the loading step of the titanium tetrachloride on the activated support in the preparation of the Ziegler-Natta catalyst which is used, a mixture of ethanol and octanol or a mixture of ethanol, butanol and octanol may then be used.
While the reaction temperature can be in the range of ambient to 120xc2x0 C., it is preferably in the range of 50xc2x0 C. to 100xc2x0 C. and most preferably in the range of 60xc2x0 C. to 90xc2x0 C.
While the pressure can be in the range of atmospheric pressure to 60 kg/cm2, it is preferably in the range of 3 kg/cm2 to 30 kg/cm2, still more preferably in the range of 4 kg/cm2 to 18 kg/cm2.
The parameters of the terpolymerization reaction of ethylene, 1-pentene and 1-octene in the slurry phase polymerization may be such that the resultant terpolymer of ethylene, 1-pentene and 1-octene satisfies the requisites or properties hereinbefore set out for such a terpolymer.
In another embodiment of the slurry polymerization process, the further xcex1-olefin may differ, as regards its total number of carbon atoms, by more than 1 unit from 1-pentene, and is not 1-octene.
In the loading step of the titanium tetrachloride on the activated support in the preparation of the Ziegler-Natta catalyst which is used, a mixture of ethanol and the alcohol with the same number of carbon atoms as with the third alpha olefin may be used, or a mixture of ethanol, pentanol and the alcohol with the same number of carbon atoms as with the third alpha olefin may be used.
While the reaction temperature can be in the range of ambient to 120xc2x0 C., it is preferably in the range of 50xc2x0 C. to 100xc2x0 C. and most preferably in the range of 60xc2x0 C. to 90xc2x0 C.
While the pressure can be in the range of atmospheric pressure to 60 kg/cm2, it is preferably in the range of 3 kg/cm2 to 30 kg/cm2, still more. preferably in the range of 4 kg/cm2 to 18 kg/cm2.
In another embodiment of the fourth and fifth aspects of the invention, as well as in an embodiment of the sixth aspect of the invention, a gas phase polymerization process is used.
In other words a gas or vapour phase process is employed to obtain particular terpolymers of ethylene/1-pentene and a further alpha olefin.
When vapour phase polymerization is used, the catalyst may also be in solid form, and preferably comprises a Ziegler-Natta catalyst. Thus, the ethylene, 1-pentene and to further xcex1-olefin will be polymerized in vapour phase in the presence of the Ziegler-Natta catalyst or catalyst system in solid form, eg solid particulate form.
Any suitable Ziegler-Natta catalyst for ethylene polymerization in vapour phase can, at least in principle, then be used. More particularly a silica supported catalyst, a prepolymerized catalyst or a polymer diluted catalyst may be used. A catalyst system comprising a titanium based Ziegler Natta catalyst and, as co-catalyst, an organo aluminium compound, is preferred. Most preferred are a prepolymerized titanium catalyst and a polymer diluted titanium catalyst.
The catalyst may be that obtained by contacting activated anhydrous or partially anhydrized magnesium chloride with titanium tetrachloride in the presence of a plurality of alcohols as described above, with this catalyst then being further prepolymerized or polymer diluted.
Thus, in one particular case of this aspect of the vapour phase polymerization, a prepolymerized catalyst obtained by contacting a catalyst obtained from activated anhydrous magnesium chloride with titanium tetrachloride in the presence of a plurality of alcohols, with an xcex1-olefin, can be used.
For the prepolymerization, xcex1-olefins of 2 to 8 carbon atoms are preferred. The amount of polymer resulting from the prepolymerization is preferably in the range of 1 to 500 g polymer/g of catalyst. Two case regarding the amount of prepolymer obtained after the prepolymerization can be distinguished:
an amount of 2-5 g of prepolymer/g of catalyst an amount of 6-500 g of prepolymer/g of catalyst
More particularly the prepolymer may be that obtained by terpolymerizing a mixture of ethylene, 1-pentene and a third xcex1-olefin.
The Inventors surprisingly discovered that different terpolymers are obtained in the vapour phase terpolymerization according to this invention when (i) the third xcex1-olefin differs, as regards its total number of carbon atoms, by more than 1 unit from 1-pentene; or (ii) the third xcex1-olefin differs, as regards its total carbon atoms, by 1 unit from 1-pentene and has more carbon atoms than 1-pentene; or (iii) the third xcex1-olefin differs, as regards its total carbon atoms, by 1 unit from 1-pentene and has fewer carbon atoms than 1-pentene.
The Inventors further surprisingly discovered that different terpolymers are obtained in the vapour phase terpolymerization process according to this invention if the prepolymer is obtained by terpolymerization as described above and the alpha olefins are employed in different proportions in the terpolymerization in order to obtain a prepolymer with different alpha olefin content. In the prepolymer formation, the ratio of the molar proportion of ethylene to the sum of the molar proportions of 1-pentene and the further xcex1-olefin may be between 99,9:0,1 and 90:10.
The ratio of the molar proportion of 1-pentene to that of the further xcex1-olefin may be between 0,01:99,99 and 99,99:0,01. The preferred third xcex1-olefin content in the prepolymerization, based on the 1-pentene content, is greater than 10% by mass and, more preferably, greater than 20% by mass. The most preferred prepolymers are those obtained when the prepolymer has the same alpha olefin content as the final terpolymer obtained in the vapour phase terpolymerization.
In order to obtain the prepolymer, a cocatalyst may be used together with the particular catalyst as hereinbefore described. The co-catalyst employed may be an organo aluminium compound. Typical organo-aluminium compounds which can be used are compounds expressed by the formula AlRmX3xe2x88x92m wherein R is a hydrocarbon component of 1 to 15 carbon atoms, X is a halogen atom , and m is a number represented by 0 less than mxe2x89xa63. Specific examples of suitable organo aluminium compounds which can be used are: a trialkyl aluminium, a trialkenyl aluminium, a partially halogenated alkyl aluminium, an alkyl aluminium sesquihalide, an alkyl aluminium dihalide. Preferred organo aluminium compounds are alkyl aluminium compounds, and the most preferred is triethylaluminium. The atomic ratio of aluminium to titanium in the catalyst system may be between 0,1:1 and 10000:1, preferably between 1:1 and 5000:1.
The prepolymer may be prepared in a separate stirred zone or vessel in suspension in a slurrying agent, and then supplied in slurry phase to the reaction zone in which the gas phase terpolymerization is effected, in order to terpolymerize the monomers. In this case the reaction temperature in the gas phase terpolymerization reaction zone may be sufficient for the small amount of catalyst slurrying agent to vaporize instantly at the pressure employed in the texpolymerization.
Instead, the prepolymer may be prepared or produced in a separate stirred zone or vessel in suspension in a slurrying agent and may be dried in a separate drying zone or unit provided to remove the slurrying agent from the catalyst slurry, with the resultant dry catalyst being supplied to the reaction zone in a dry form. In this case the temperature of the drying unit may be below the temperature which deactivates the prepolymer, ie the temperature above which the catalyst loses more than 10% of its activity over a period of 24 hours. The catalyst is carried to the reaction zone by means of an inert gas such as highly purified nitrogen.
Preferred slurrying or suspension agents are aliphatic or cyclo-aliphatic liquid hydrocarbons, with the most preferred being hexane and heptane.
The temperature during the prepolymerization may between xe2x88x9215 and 80xc2x0 C., but must be kept constant during the prepolymerization. The pressure may be between atmospheric pressure and 10 kg/cm2. According to this invention nitrogen or an inert gas should be present in the reaction medium in order to control the low amount of prepolymer obtained during the prepolymerization. The preferred amount of nitrogen is between 10% and 90% of the reaction gas phase present in the prepolymerization unit.
In another particular case of this aspect of the invention a polymer diluted catalyst may be used. The polymer is preferably used in powder form. The most preferred is a polymer in powder form with the same granularity as the final terpolymer. In other words a powder polymer with the same level of average particle size and/or average particle size distribution as the final terpolymer.
The polymer diluted catalyst may be that obtained by mixing a catalyst component and a polymer component. The catalyst component may be a catalyst as hereinbefore described, while the polymer component may comprise the polymer in powder for.
Any polymer inactive to the catalyst may then be used. The polymer is preferably an ethylene polymer, and the most preferred polymer is a terpolymer with the same monomer content as the terpolymer finally obtained in the gas phase polymerization according to this invention. The Inventors surprisingly discovered that any terpolymer of ethylene with 1-pentene and a third alpha olefin, which alpha olefin differs from 1-pentene by one carbon unit can be used successfully for the preparation of the polymer diluted catalyst.
The mixing of the catalyst component and the polymer component may be effected by mechanical stirring of the catalyst component with the polymer powder. Other known methods of stirring are also possible. The catalyst component may be added to the polymer powder in a powder form or in a slurry form. The Inventors found that the best results are obtained when the catalyst or catalyst component is added to a suspension of the powder polymer in an inert liquid hydrocarbon carrier liquid, the resultant slurry mixed and the carrier liquid evaporated to obtain a polymer diluted catalyst in powder form. In a particular case the polymer diluted catalyst slurry may be supplied directly to the gas phase polymerization zone provided that the temperature in the reaction zone allows immediate vaporization of the limited amount of carrier liquid of the polymer diluted catalyst.
A cocatalyst may be added to the polymer powder support prior to the addition of the catalyst or concomitantly therewith. The co-catalyst employed may be an organo aluminium compound. Typical organo-aluminium compounds which can be used are compounds expressed by the formula AlRmX3xe2x88x92m wherein R is a hydrocarbon component of 1 to 15 carbon atoms, X is a halogen atom , and m is a number represented by 0 less than mxe2x89xa63. Specific examples of suitable organo aluminium compounds which can be used are: a trialkyl aluminium, a trialkenyl aluminium, a partially halogenated alkyl aluminium, an alkyl aluminium sesquihalide, an alkyl aluminium dihalide. Preferred organo aluminium compounds are alkyl aluminium compounds, and the most preferred is triethylaluminium. The atomic ratio of aluminium to titanium in the catalyst system may be between 0,1:1 and 10000:1, preferably between 1:1 and 5000:1.
The mixing of the polymer powder with the catalyst as hereinbefore described in the presence or absence of the cocatalyst may be effected at a temperature between xe2x88x9210xc2x0 C. and 40xc2x0 C., preferably at ambient temperature.
The vapour phase reaction may be carried out in one or more stirred reaction zones, in a single stage reactor or a chain of two or more reactors, in a batch or continuous fashion, as described hereinbefore. The 1-pentene and further xcex1-olefin may be added as a mixture or separately in a prevaporized vapour phase or in liquid phase and vaporized in the reaction zone.
The preferred reactor for the terpolymerization according to this invention is a stirred reactor, ie a reactor where the gas phase reaction medium and as well the mixture of the terpolymer obtained in powder form in the gas phase reaction medium are stirred by mechanical means known in the art.
The molecular weight of the resultant random terpolymer can be regulated by hydrogen addition to the reaction zone during the reaction. The greater the amount of hydrogen added, the lower will be the molecular weight of the random terpolymer.
An inert gas may also be present in the polymerization zone. Examples of inert gas according to this invention are highly purified nitrogen or argon with nitrogen being the most preferred.
In one embodiment of this aspect of the invention the presence of the nitrogen is not only possible but also desirable. In this case the nitrogen acts as a diluting agent for the gas polymerization medium and thereby controls the activity of the catalyst during the gas phase terpolymerization.
The parameters of the gas phase terpolymerization reaction of ethylene, 1-pentene and the further xcex1-olefin may be such that the resultant terpolymer of ethylene, 1-pentene and the further xcex1-olefin complies with the properties or requisites hereinbefore described in the first, second and third aspects of the invention.
The molecular weight distribution, ie the polidispersity index, n, as obtained from the ratio of the weight molecular weight and number molecular weight by nomenclature and measurements methods known in the literature, of such terpolymers can vary widely according to the particular prepolymerized catalyst employed.
In one embodiment of this aspect of the invention the polydispersity index of the terpolymer according to this invention is greater than 4.
However, in another embodiment of this aspect of the invention the polydispersity index of the terpolymer according to this invention is smaller than 4.
In yet a further embodiment of the fourth, fifth and sixth aspects of the invention, a solution phase polymerization is used.
When solution phase polymerization is used, the catalyst system may be soluble or insoluble in a liquid reaction medium, with the monomers and terpolymer being dissolved in the reaction medium throughout the polymerization reaction.
The liquid reaction medium may be a hydrocarbon or mixture of hydrocarbons selected such that the terpolymer is soluble therein at the reaction temperature. As an example, when cyclohexane is used as the liquid reaction medium, the reaction temperature should be higher than 90xc2x0 C. to obtain dissolution of the terpolymer therein.
It is preferred to perform the solution polymerization just above the lowest temperature where the terpolymer is completely soluble in the liquid reaction medium.
The preferred temperature to perform the solution polymerization according to this invention is below 120xc2x0 C., or even below 100xc2x0 C.
In one embodiment of the invention, when solution phase polymerization is used, the catalyst system may comprise a catalyst used for solution polymerization of ethylene. In principle, any catalyst for solution copolymerization of ethylene with xcex1-olefins may be used. The catalyst may thus be a vanadium catalyst such as VCl4 or VOCl3; a titanium catalyst, such as a titanium tetrachloride catalyst or a solubilized titanium trichloride catalyst; or a mixture of such a titanium catalyst and such a vanadium catalyst.
More preferably the catalyst may be that obtained by contacting activated magnesium chloride with titanium tetrachloride in the presence of a mixture of alcohols as described above.
Most preferably the catalyst may be that obtained by contacting activated magnesium chloride with titanium tetrachloride in the presence of a mixture of alcohols as described above, providing that in the loading step of the titanium tetrachloride on the activated support or magnesium chloride in the preparation of the Ziegler-Natta catalyst which is used, a mixture of ethanol and the alcohol with the same number of carbon atoms as the third alpha olefin or a mixture of ethanol, pentanol and the alcohol with the same number of carbon atoms as the third alpha olefin, is used.
The most preferred catalyst for the solution terpolymerization according to this invention is a catalyst with an activity higher than 10 g terpolymer/mg of Ti content in the catalyst.
Particular aspects of the solution phase polymerization according to this invention are whether the catalyst system is supplied to the reaction zone at xe2x80x9cthe optimum ageing timexe2x80x9d, or at xe2x80x9cconstant activity timexe2x80x9d as previously described.
Thus in a particular case of the embodiment of the solution phase polymerization in the process aspect of the invention, a cocatalyst may be used, and the cocatalyst supplied first to the reaction zone in which the terpolymerization is being effected, and then the catalyst after a period of time. In another particular case of this aspect of the invention the cocatalyst is supplied simultaneously with the catalyst to the reaction zone. In both these cases, the residence time of the reaction mixture preferentially selected to be below LAT.
In still another case of this aspect of the invention, the catalyst system may be prepared in a separate catalyst activation unit and is supplied to the reaction zone at OAT. In this case the sum of the residence time of the catalyst in the activation unit and the residence time of the catalyst in the reaction unit may be preferentially selected to be below LAT. When the reaction is carried out in a plurality of reaction zones, which may be provided in a single stage reactor vessel or by a chain of two or more reaction vessels, then two cases of this particular aspect of the invention can be distinguished.
In one particular case, the sum of the residence time of the catalyst in the activation unit and the residence time of the catalyst in the first reaction zone may be OAT+TR1, where TR1 is the time elapsed since OAT to the moment the catalyst reaches a decrease of activity of less than 25% of the activity at OAT.
In another particular case, the sum of the residence time of the catalyst in the activation unit and the residence time of the catalyst in the first reaction zone may be OAT+TR2, where TR2 is the time selected such that OAT+TR2 is less than LAT, preferentially less than xc2xd LAT and provided that the sum of the residence time of the catalyst in the activation unit and the residence time of the catalyst in all reaction zones is less than LAT.
In still another particular case of this aspect of the invention the catalyst system prepared in a separate catalyst activation unit is supplied to the reaction zone at CAT. In these cases the sum of residence time of the catalyst in the activation unit and the residence time of the catalyst in the reaction unit may be preferentially selected to be less than LAT.
In another embodiment of this aspect of the invention, the catalyst system is supplied to the reaction zone at any other time less than LAT providing that the sum of the residence time of the catalyst in the activation unit and the residence time of the catalyst in all reaction zones is less than LAT.
The parameters of solution terpolymerization reaction of ethylene, 1-pentene and a further xcex1-olefin may be such that the resultant terpolymer of ethylene, 1-pentene and the further xcex1-olefin complies with the properties or requisites hereinbefore described in the first, second and third aspects of the invention.
The molecular weight distribution of such terpolymers can vary widely according to a particular catalyst employed.
In one embodiment of this aspect of the invention, the polydispersity index of the terpolymer according to this invention is higher than 3.
In another embodiment of the invention, when solution phase polymerization is used, the catalyst or catalyst system may comprise a metallocene catalyst. Any suitable metallocene catalyst for ethylene polymerization in solution can, at least in principle, then be used. Examples of metallocenes which can be used are Group IV transition metallocenes (titanocenes, zirconocenes, hafnocenes), which are characterized by two bulky cyclopentadienyl (Cp) or substituted cyclopentadienyl ligands (Cpxe2x80x2), metallocenes with two Cpxe2x80x2 ligands arranged in a chiral array and connected together with chemical bonds by a bridging group, and cationic metallocenes. Preferred metallocene catalysts are (CpR)2ZrX2 catalysts, where R is H, Me (methyl), Et (ethyl), Pr (propyl), i-Pr, Bu (butyl), i-Bu, SiMe3, and X is Cl.
The metallocene catalyst can be used as part of a catalyst system containing also a co-catalyst which activates the metallocene. Examples of such co-catalysts are alumoxanes such as methyl alumoxane (MAO), ethyl alumoxane (EAO), and isobutylalumoxane.
In one embodiment of this aspect of the invention the terpolymerization is performed in the presence of one of the preferred metallocene (CpR)2ZrX2 catalysts, where R is H, Me (methyl), Et (ethyl), Pr (propyl), i-Pr, Bu (butyl), i-Bu, SiMe3, and X is Cl and with MAO as co-catalyst.
In another embodiment of this aspect of the invention the terpolymerization is performed in the presence of one of the preferred metallocene (CpR)2ZrX2 catalysts, where R is H, Me (methyl), Et (ethyl), Pr (propyl), i-Pr, Bu (butyl), i-Bu, SiMe3, and X is Cl and with EAO as co-catalyst.
Different methods of adding the cocatalyst can be distinguished:
mixing the metallocene catalyst with the cocatalyst under inert conditions in an inert solvent and bringing the activated complex catalyst formed into the terpolymerization reaction zone prior or continuously during the terpolymerization;
mixing the cocatalyst with a solvent provided for the polymerization, and thereafter introducing the catalyst to form the catalyst complex prior to the terpolymerization;
continuously supplying the catalyst and the cocatalyst to the reaction zone during the polymerization with the formation of the activated complex during the terpolymerization.
The parameters of metallocene terpolymerization reaction of ethylene, 1-pentene and the further xcex1-olefin may be such that the resultant terpolymer of ethylene, 1-pentene and the further xcex1-olefin complies with the properties or requisites as hereinbefore described in the first, second and third aspects of the invention.
The molecular weight distribution of such terpolymers can vary according to a particular metallocene catalyst employed, a particular co-catalyst employed and a particular mixture of alpha olefins employed.
In one embodiment of this aspect of the invention the polydispersity index of the terpolymer according to this invention is lower than 3.
According to a seventh aspect of the invention, there is provided a method of making a prepolymerized catalyst, which includes polymerizing an olefin having a carbon number between 2 and 8, in the presence of a catalyst obtained by
mixing an ether having a total number of carbon atoms equal to or greater than 8, with a partially anhydrised magnesium chloride having a water content of 0,02 mole to 2 mole of water per 1 mole of magnesium chloride at a temperature of 40xc2x0 C. to 140xc2x0 C., to produce a partially activated magnesium chloride;
adding, dropwise, an alkyl aluminium compound to the partially activated magnesium chloride in order to obtain unwashed activated magnesium chloride;
washing the activated magnesium chloride with an inert hydrocarbon liquid to obtain an activated magnesium chloride-containing slurry;
mixing a plurality of alcohols with the activated magnesium chloride-containing slurry to obtain an activated support/alcohol complex; and
mixing titanium tetrachloride with the activated support/alcohol complex, to form the catalyst.